import java.awt.*;
import java.net.*;
import java.io.*;
import java.util.*;

/**
 * Description:
 * <br/>Copyright (C), 2008-2010, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee kongyeeku@163.com
 * @version  1.0
 */
public class UdpClient
{
	//定義發(fā)送數(shù)據(jù)報(bào)的目的地
	public static final int DEST_PORT = 30000;
	public static final String DEST_IP = "127.0.0.1";

	//定義每個(gè)數(shù)據(jù)報(bào)的最大大小為4K
	private static final int DATA_LEN = 4096;
	//定義該客戶(hù)端使用的DatagramSocket
	private DatagramSocket socket = null;
	//定義接收網(wǎng)絡(luò)數(shù)據(jù)的字節(jié)數(shù)組
	byte[] inBuff = new byte[DATA_LEN];
	//以指定字節(jié)數(shù)組創(chuàng)建準(zhǔn)備接受數(shù)據(jù)的DatagramPacket對(duì)象
	private DatagramPacket inPacket = 
		new DatagramPacket(inBuff , inBuff.length);
	//定義一個(gè)用于發(fā)送的DatagramPacket對(duì)象
	private DatagramPacket outPacket = null;
	public void init()throws IOException
	{
		try
		{
			//創(chuàng)建一個(gè)客戶(hù)端DatagramSocket，使用隨機(jī)端口
			socket = new DatagramSocket();
			//初始化發(fā)送用的DatagramSocket，它包含一個(gè)長(zhǎng)度為0的字節(jié)數(shù)組
			outPacket = new DatagramPacket(new byte[0] , 0 ,
				InetAddress.getByName(DEST_IP) , DEST_PORT);
			//創(chuàng)建鍵盤(pán)輸入流
			Scanner scan = new Scanner(System.in);
			//不斷讀取鍵盤(pán)輸入
			while(scan.hasNextLine())
			{
				//將鍵盤(pán)輸入的一行字符串轉(zhuǎn)換字節(jié)數(shù)組
				byte[] buff = scan.nextLine().getBytes();
				//設(shè)置發(fā)送用的DatagramPacket里的字節(jié)數(shù)據(jù)
				outPacket.setData(buff);
				//發(fā)送數(shù)據(jù)報(bào)
				socket.send(outPacket);
				//讀取Socket中的數(shù)據(jù)，讀到的數(shù)據(jù)放在inPacket所封裝的字節(jié)數(shù)組里。
				socket.receive(inPacket);
				System.out.println(new String(inBuff , 0 , 
					inPacket.getLength()));
			}
		}
		//使用finally塊保證關(guān)閉資源
		finally
		{
			if (socket != null)
			{
				socket.close();
			}
		}
	}

	public static void main(String[] args) 
		throws IOException
	{
		new UdpClient().init();
	}
}